1. Field of the Invention
This invention relates to a method of processing the mixed fiber stream obtained from the corn wet-milling process to make a product having a high total dietary fiber content.
2. Description of Related Art
In recent years, there has been an increasing awareness of the role that fiber plays in the human diet. This stems not only from the role that fiber plays as a bulking agent, but also from the role it is believed to play in preventing diseases of the gastrointestinal tract.
The dietary fiber from wheat, wheat bran, has been consumed in breakfast cereals, whole wheat breads, and similar products for many years. However, there is a recognized need for larger amounts of fiber to supplement processed foods which are now consumed by a large proportion of the population. For these reasons, food suppliers have sought additional sources of dietary fiber.
One potential source of dietary fiber is the corn fiber obtained as a by-product of the wet milling of corn. However, this product contains fairly high percentages of starch and protein. Such additional components make the fiber less suitable for use in baking and other food applications. This has led workers to look for an economical and commercially acceptable process to reduce the amount of starch and protein while increasing the dietary fiber content of the fiber obtained from the corn wet-milling process.
In U.S. Pat. No. 4,181,534, a process is disclosed for treating the wet fiber stream obtained from the corn wet-milling process. According to the process, the fiber stream, while still wet, is abraded by means of a beater or impact mill. The milled product is then separated into fractions with one fraction being an enriched fiber containing a high proportion of pentosans.
A process for enriching the fiber obtained from corn and soybeans is disclosed in U.S. Pat. No. 4,181,747. In this process, the crude fiber is heated with dilute aqueous acid to hydrolyze and dissolve undesired by-products. The material is then washed extensively in order to obtain a fiber of higher dietary fiber content.
U.S. Pat. No. 4,757,948 discloses a process for producing a high total dietary corn fiber by a two-step process which employs first a sifter and then a roller mill. The fiber fraction obtained in accordance with this process has from about eighty to eighty-five percent total dietary fiber.
Although these prior processes can give an enriched fiber product, there is still a need for a simple low-cost process for commercially producing a product of high dietary fiber content from corn. We have now discovered a simple and economical process for enriching the dietary fiber content of corn fiber without the need for a chemical hydrolysis or for an expensive milling operation. By this process, the corn wet-miller can convert in a continuous, high-yield process a low-value by-product to a food component of much higher value. Moreover, with further process refinements, the dietary fiber can be produced with a very low sulfur dioxide (SO.sub.2) content.